Heat control for kiln



Nov. 7, 1967 A. R. MARTIN 3,351,331

HEAT CONTROL FOR KILN Filed Dec. 28, 1965 FIG. I

INVENTOR ALBERT RAY MARTIIYN United States Patent 3,351,331 HEAT CONTROL FOR KILN Albert Ray Martin, 2503 37th, Snyder, Tex. Filed Dec. 28, 1%5, Ser. No. 516,951 Claims. (Cl. 263-40) ABSTRACT OF THE DISCLOSURE This invention relates to kilns and more particularly to a heat control for a kiln.

An object of this invention is to provide a heat control for a kiln.

Another object is to provide a control which keeps a large kiln at uniform temperature throughout the space of the kiln.

A further object is to provide a heat control that will maintain a large kiln at a uniform temperature throughout an extended period of time.

Yet another object is to provide a heat control which will maintain a large kiln at a uniform temperature regardless of change of conditions, such as change in ambient temperature or change of wind direction or change in wind velocity or change in humidity, etc.

Yet another object is to provide a heat control which will failsafe; i.e., in event of failure, it will not result in damage to ware or kiln;

Still further objects are to achieve the above with a system that is sturdy, compact, durable, simple, safe, versatile, and reliable, yet inexpensive and easy to manufacture and operate.

Still further objects are to achieve the above with a method that is inexpensive and does not require skilled people to install, adjust and operate.

The specific nature of the invention, as well as other objects, uses, and advantages thereof, will clearly appear from the following description and from the accompanyin g drawing, in which:

FIG. 1 illustrates schematically the control for two burner units.

FIG. 2 illustrates schematically the use of a plurality of burner units and transmitting thermometers for a large kiln.

Typical of the environment wherein this invention would be used would be controlling the heat for a kiln 10. Typically, this kiln would be 62 x 12 x 9 feet and contain 30,600 brick at one firing. It is necessary that the kiln be maintained at 1800 F. :10 F. for twelve hours. If the temperature varies in different parts of the furnace, a nonuniform product will result-which is undesirable. In fact, it is actually more desirable to maintain the temperature to a range of :5 F. Also, brick kilns are often located in remote areas where electrical power is undependable; therefore, it is desirable to provide a system so that the temperature will not fluctuate wildly in case of a power failure to the control unit. A wildly-fluctuating temperature would result not only in spoilage of the ware but damage to the kiln.

Further, by Way of example, the unit is particularly adapted to be used in a kiln where the brick are preheated before entering a closed furnace for firing. Such a kiln 3,351,331 Patented Nov. 7, 1967 ICC is described in my copending application, executed on Dec. 11, 1965, and filed on Dec. 15, 1965, Ser. No. 514,087, and is also basically outlined in the trade journal Brick and Clay Record, vol. 147, No. 1, July 1965, at page 32, published in Chicago, Illinois, by Cahners Publishing Company, Inc.

The kiln 10 is heated by thirty gas burners 12. The burners are grouped in units of three so that there are ten units 14 of burners. Each unit has unit supply pipe 16. Also, there is one transmitting thermometer 18 in the form of a thermocouple within the kiln 10 for each unit 14. Each transmitting thermometer 18 is placed in the kiln at a location which is affected by the heat from the corresponding unit; i.e., there are ten transmitting thermometers 18 in the kiln and each of them is located in the kiln so that the temperature detected by the thermometer is primarily related to one of the units 14.

Each of the supply pipes 16 is fed from a valve unit 20 which contains two paths. Each of the valve units 20 includes a low fire bypass passageway, or first path, which includes manual valve 22 and orifice 24. A parallel loop, or second path, contains high fire automatic valve 26. Each of the valves 26 is an electrical solenoid valve having a normal olf position. Upon energizing the solenoid, the valve is in the on position. The valve has only the two positions-on or off; i.e., it is not a proportioning valve. In case of power failure, there can be no energization of the solenoid and, therefore, valve 26 will go to the ofi. position. The valve units 20 are supplied by fuel gas under pressure from gas main 28.

Each transmitting thermometer 18 is connected to one automatic valve 26 which controls the burner unit '14 through controller 30.

According to my invention, the main fuel flow is through the orifice 24 because the size of pipe and valve 26 restrict the fuel flow through that path; e.g., according to one satisfactory design, 1850 units of fuel would pass through the orifice 24 while 350 units of fuel pass through the control valve 26 when it is open. Stated otherwise, when the automatic valve 26 is open, approximately 84% of the fuel is supplied through the orifice 24 and 16% of the fuel is supplied through the automatic valve 26. Another way of expressing the relationship is that, when the automatic valve 26 changes from the closed to the open position. The fuel flow to the kiln increases by 19%.

I have found that the most satisfactory way of setting this relationship is to choose an orifice size 24 so that, With an automatic valves 26 closed, the kiln temperature is maintained at about 1780" F., which is 20 F. less than the desired temperature.

Although the temperature maintained within the kiln is below the desired range of maintaining the kiln, it is still high enough to prevent absolute spoilage of the ware and damage to the furnace. Therefore, if a power failure occurs, all of the automatic valves 26 are closed and the kiln temperature will drop slightly. However, inasmuch as the blowers (not shown) will also probably be inactivated due to the power failure, the temperature drop may not be so drastic. It will be noted that, even with the blowers inactivated, there will be a natural draft flow of circulation through the kiln. Experience with this control unit has been that it is sufficiently dependable to leave it in operation unattended at night.

Analysis of the system will reveal that the temperature of the kiln is maintained principally by the flow gas to the orifice 24. Only when some area of the kiln is reduced slightly in temperature does the controller actuate one of the valves 26 to provide additional fiow of gas to the cool area. The activation of one of the ten valves 26 will be upon a random basis and there will be no abrupt change which would abruptly change the draft upon the kiln.

Furthermore, although each of the burner units 14 controls the temperature in one particular area, of the kiln 10, there is naturally an interaction, i.e., if one burner unit 14 is on high heat, it will tend to increase the temperature in the adjacent areas. Also, if one side of the kiln tends to be cooler than the other because of higher wind, increased fuel to that side will still maintain uniform temperature throughout all areas of the kiln.

The large number of controlled burner units is economically possible because of the low cost of each.

The controller 30 may be set to a higher temperature than 1800 F. for different product, in which event the orifices may be changed at the option of the operator.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction, materials, and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. A heat control system for a kiln comprising:

(a) a plurality of spaced burner units,

(b) each burner unit heating an area of the kiln and (c) each burner unit including at leastone burner,

(d) a unit fuel pipe to each burner unit,

(e) a transmitting thermometer for each burner unit in the kiln in the area which the burner unit heats,

(f) a main fuel pipe supplying fuel to the burner units,

(g) a first fuel path for each burner unit from the main fuel pipe to each unit fuel pipe,

(h) a second fuel path for each burner unit from the main fuel pipe to each unit fuel pipe,

(j) means in the second fuel path for restricting the fuel flowing in the second fuel path to less than the fuel flowing in the first fuel path, and

(k) means in the second fuel path for opening and closing the second fuel path responsive to the transmitting thermometer for that burner unit.

2. The invention as defined in claim 1 wherein (In) said means for opening and closing the second fuel path has two positions only,

(i) one position completely open and (ii) the other position completely closed.

3. The invention as defined in claim 1 wherein (m) said means for restricting the fuel restricts the flow of the fuel in the second path to less than onethird of the flow of the fuel in the first path.

4. The invention as defined in claim 1 wherein (m) the first fuel path has sufficient fuel-carrying capacity to maintain the kiln at a minimum tempera ture high enough to prevent spoilage of ware in the kiln and damage to the kiln in the event the second path is closed by malfunction.

5. The invention as defined in claim 4 wherein (n) said minimum temperature is about 1780 F.

6. A heat control system for a kiln comprising:

(a) a plurality of spaced burner units,

(b) each burner unit heating an area of the kiln and (c) each burner unit including at least one burner, (d) a main fuel pipe supplying fuel,

(e) a unit fuel pipe for each burner unit connecting each burner unit with the main fuel pipe,

(f) a transmitting thermometer for each burner unit in the kiln in the area which the burner unit heats,

(g) a valve in each unit fuel pipe,

(h) means attached to each valve for opening each valve responsive to the measured temperature of the subject area, and

(j) a bypass passageway connecting the main fuel pipe to each burner unit,

(k) said bypass passageway having greater fuel-carrying capacity than. the passageway through said valve.

7. The invention as defined in claim 6 wherein (m) said means for opening each valve has two positions only,

(i) one position completely open and (ii) the other position completely closed.

8. The invention as defined in claim 6 wherein (m) the fuel-carrying capacitythrough said valve is less than one-third the fuel-carrying capacity through said by-pass passageway.

9. The invention as defined in claim 8 wherein (n) the fuel-carrying capacity through the bypass passageway is sufficient to maintain the kiln at a minimum temperature high enough to prevent spoilage of ware in the kiln and damage to the kiln in the event the valve is closed by malfunction.

10. The method of controlling the temperature in a kiln having a plurality of spaced heat units, each heat unit heating an area of the kiln, comprising:

(a) supplying energy to each heat unit at one of two rates at all times,

(i) the first rate sufficient to maintain the kiln at sufficient temperature to prevent spoilage of the ware and damage to the kiln,

(iii) the second rate being no more than one-third greater than the first rate,

(b) measuring the temperature in each of the individual areas of the kiln, and

(c) supplying energy at one of the two rates to the individual heat units, responsive to the measured temperature of the area heated by the subject heat unit.

References Cited UNITED STATES PATENTS 1,615,478 1/1827 Poole 236-15 2,518,996 8/1950 Peckham 236-15 3,244,219 5/1966 Nesbitt 236-15 FREDERICK L. MATTESON, JR., Primary Examiner.

JOHN J. CAMBY, Examiner. 

1. A HEAT CONTROL SYSTEM FOR A KILN COMPRISING: (A) A PLURALITY OF SPACED BURNER UNITS, (B) EACH BURNER UNIT HEATING AN AREA OF THE KILN AND (C) EACH BURNER UNIT INCLUDING AT LEAST ONE BURNER, (D) A UNIT FUEL PIPE TO EACH BURNER UNIT, (E) A TRANSMITTING THERMOMETER FOR EACH BURNER UNIT IN THE KILN IN THE AREA WHICH THE BURNER UNIT HEATS, (F) A MAIN FUEL PIPE SUPPLYING FUEL TO THE BURNER UNITS, (G) A FIRST FUEL PATH FOR EACH BURNER UNIT FROM THE MAIN FUEL PIPE TO EACH UNIT FUEL PIPE, (H) A SECOND FUEL PATH FOR EACH BURNER UNIT FROM THE MAIN FUEL PIPE TO EACH UNIT FUEL PIPE, (J) MEANS IN THE SECOND FUEL PATH TO LESS THAN THE FUEL FLOWING IN THE SECOND FUEL PATH TO LESS THAN THE FUEL FLOWING IN THE FIRST FUEL PATH, AND (K) MEANS IN THE SECOND FUEL PATH FOR OPENING AND CLOSING THE SECOND FUEL PATH RESPONSIVE TO THE TRANSMITTING THERMOMETER FOR THAT BURNER UNIT. 